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Chemical mixtures and the ‘cocktail effect'

Chemistry is a fundamental part of life and our existence. We have always been exposed to natural chemicals. Recently, along with technological developments and evolution, we are exposed to increasing amounts of man-made chemicals from a variety of sources. We are exposed to them throughout our lives. They are contained in food, water, medicines, air, cosmetics, health care products, clothing and other consumer products. In the natural environment, all living organisms are exposed to a complex cocktail of chemical substances.

This exposure to a variety of chemicals is sometimes known as the "cocktail effect". This ‘cocktail effect' is where different chemicals have combined adverse effects either on humans or the environment.

There are three different situations where we may be exposed to chemical cocktails:

A product that we use can be a mixture of different chemicals. Therefore, we and the environment are exposed to these different chemicals, all at the same time.

We can be exposed to a single chemical coming from different sources at different times. This can result in a much bigger exposure over time for humans or the environment to that single chemical.

Different chemicals from different sources released at different times and from different places can combine to expose humans or the environment to a cocktail of chemicals.

For scenarios (2) and (3), we need to understand how chemicals get released from the different sources and how they combine to result in human and environmental exposure.

For scenario (1), any adverse effect may be due to the mixture as a whole or to the separate individual chemicals. A complicating factor is that the individual chemicals may become more hazardous simply because of the other chemicals they are mixed with.

Currently, we assess the hazards and risks of chemicals based on the evaluation of single substances. The assessments include some safety margins to take account of uncertainties. However, there are concerns that analysing individual chemicals alone does not provide sufficient security and that the combination effects of chemicals should be addressed in a more systematic way.

At the moment, there is not a general legal requirement for industry to assess the combination of effects and the risks of various chemicals due to combined exposure. However, there are developments on how this can be addressed. Where a group of chemicals are known or assumed to cause similar effects and the exposure is wide, it may be possible to conduct a combined risk assessment. ECHA is following the developments in this area and encourages industry to analyse the need for combined hazard and risk assessment for the chemicals they produce.